hmm.. figure this one out

Supposing that eleven coins with round holes are worth 15 bits, while eleven square ones are worth 16 bits, and eleven of triangular shape are worth 17 bits, tell how many round, square or triangular pieces of cash would be required to purchase an item worth eleven bits. a friend solved it easily (or so he claimed), but I stared at it for ten minutes. Struggled for 10 minutes. gave ut.

Yup. Each coin is worth x/11 - round is 15/11, square is 16/11, triangle is 17/11. The elevenths make things a little mind-bending, so to get to units, figure out how many elevenths you need... 11 = 121/11. So the answer is equivalent to adding up multiples of 15, 16 and 17 to get to 121. Well, eight round coins is eight times 15 is 120, one too few. Simply upgrade one round to a square and the answer is revealed. About a minute. Took longer to type this. Joe